The present invention relates to clutches in general, and more particularly to improvements in methods of and in apparatus for engaging and disengaging clutches, especially friction clutches in the power trains of motor vehicles. Still more particularly, the invention relates to improvements in methods of and in apparatus for regulating the supplying of electric current to current-consuming component parts of clutch actuating means.
The arrangement which serves to engage and disengage the friction clutch in the power train of a motor vehicle often comprises current-consuming parts (e.g., parts including an electric motor) which initiate the engagement, or a change of the extent of engagement, of the clutch between the prime mover (such as an internal combustion engine) and the change-speed transmission in the power train of the vehicle. It is often necessary to supply to such current-consuming parts a certain amount of electric current (called rest current or remaining or remanent current) which amounts to a small fraction of maximum current (e.g., about 7 percent of maximum current) and the purpose of which is to avoid a resetting of the clutch actuating assembly or arrangement while the clutch is engaged. A reason for the tendency of the clutch actuating assembly to cause a resetting of the clutch is that, in many instances, such assembly employs a component part (e.g., a worm wheel gearing) which is actuatable by an electric motor and which is not entirely self-locking, i.e., it tends to effect an undesirable resetting of the clutch, e.g., at a time and under circumstances when a resetting is not only undesirable but can be dangerous to the occupant(s) of the motor vehicle. The purpose of the supplying of rest current to the current-consuming component(s) of the clutch actuating assembly is to prevent uncontrolled changes in the setting of the parts (such as the aforementioned worm wheel gearing) which are actuatable by the current-consuming components but exhibit a tendency to reset the clutch in the absence of an opposition from the current-consuming parts.
An object of the instant invention is to provide a novel and improved apparatus for regulating the supplying of rest current to one or more current-consuming parts which, when supplied with current, can oppose undesirable changes in the condition of clutch actuating means.
Another object of this invention is to provide a novel and improved method of regulating the supplying of electric current to one or more constituents of a clutch actuating assembly in the power train of a motor vehicle or the like.
A further object of the invention is to provide a power train which embodies a friction clutch and a rest current regulating apparatus of the above outlined character.
An additional object of the present invention is to provide a novel and improved method of preventing undesirable changes in the condition (extent of engagement) of a friction clutch in the power train of a motor vehicle.
Still another object of the invention is to provide a power train wherein an adjustable clutch can regulate the transmission of torque between a prime mover and a gearbox and wherein the setting of the clutch is less likely to change at an inopportune time than in presently known power trains.
A further object of the invention is to provide a novel and improved method of regulating the supplying of so-called rest current to an electric motor in a clutch actuating mechanism.
Another object of the invention is to provide a method which renders it possible to prevent uncontrolled or unsatisfactory or undesirable changes in the extent, especially relatively small extent, of engagement or disengagement of a clutch in the power train of a motor vehicle.
One feature of the present invention resides in te provision of an apparatus for manipulating the aforediscussed rest current in an actuator for a force exerting clutch. The improved apparatus comprises a source (e.g., at least one battery) of rest current, at least one consumer of rest current (e.g., an electric motor), at least one resilient element (e.g., a coil spring) which is arranged to act upon the actuator in a sense to oppose the force being exerted by the clutch, and means for effecting the application of rest current to the at least one consumer when the bias of the at least one resilient element upon the actuator exceeds the force being exerted by the clutch.
The means for effecting the application of rest current can include at least one sensor which is arranged to monitor at least one of a plurality of parameters including (a) the bias of the at least one resilient element and (b) the force being exerted by the clutch.
The actuator can include a worm wheel gearing which is interposed between the at least one consumer of rest current and the at least one resilient element.
The clutch can be arranged to transmit torque between a prime mover (such as an internal combustion engine) and a gearbox (also called change-speed transmission) in the at least partly engaged condition of the gearbox and includes a member (e.g., a lever) which is pivotable in a first direction by the at least one resilient element and in a second direction (such as counter to the first direction) by the at least one consumer of rest current. The relationship between the bias of the at least one resilient element upon the actuator and the extent of pivoting of the aforementioned member of the clutch is or can be a linear relationship.
Another feature of our invention resides in the provision of a method of situation-dependent regulation of rest current in an actuator for a force-applying clutch. The method comprises the steps of activating the application of rest current to thus assist the retention of the actuator in a sense to disengage the clutch, monitoring the bias of at least one resilient element (such as the aforementioned coil spring) acting upon the actuator, and switching off the rest current when the bias of the at least one resilient element upon the actuator exceeds the force being applied by the clutch.
The arrangement is or can be such that the activating step is carried out only during (a) starting of a motor vehicle having a power train which embodies the clutch, and (b) during shifting of a gearbox forming part of the power train.
The step of switching off the rest current can be carried out abruptly when the bias of the at least one resilient element exceeds the force being applied by the actuator upon a mobile member (such as the aforementioned lever) of the clutch against the opposition of the at least one resilient element.
The activating step can include abrupt application of rest current when the bias being applied by the at least one resilient element exceeds by a first threshold value that force which is being applied to the actuator by the clutch, and abrupt interruption of application of rest current when the bias of the at least one resilient element thereupon decreases to a second threshold value. The arrangement can be such that the first threshold value is reached when the bias of the at least one resilient element exceeds the force which the actuator applies to the at least one resilient element.
The activating step can be carried out by resorting to a ramp, a parabola, an exponential function, a polynomial of nth order or the like.
The step of switching off the rest current can be carried out abruptly in a sense to engage the clutch, and such step can include reversing the direction of current flow.
It is also within the purview of the present invention to abruptly carry out the activating step as well as the switching off step, and the switching off step can be followed by a step of reversing the direction of current flow to thus engage the clutch. The reversing step is or can be carried out after a mobile member (such as the aforementioned lever) of the actuator completes the travel through a predetermined distance.
The activating step can be carried out by way of a ramp, and the step of switching off the rest current can be carried out by way of a ramp in a sense to engage the clutch by reversing the direction of current flow.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claim. The improved apparatus itself, however, both as to its construction and the modes of assembling, installing and operating the same, together with numerous additional important and advantageous features and attributes thereof, wil be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.